Apparatus for expanding and elongating tubular work pieces



Dec. 24, 1935. B BANNISTER 2,925,147

APBARATUS FOR EXPANDING AND. ELONGATING TUBULAR WORK PIECES.

Filed March 14, 1933 2 Sheets-Sheet 1 Dec. 24, 1935.

bwerd'or: Esra/v7 Patented Dec. 24, 1935 PATENT OFFICE APPARATUS FOR EXPANDING AND ELON- GATING TUBULAR WORK PIECES Bryant Bannister, Mount Lebanon, Pa.

Application March 14, 1933, Serial No. 660,717

1 Claim. (01. 80-13) This invention relates to the manufacture of seamless pipes and tubes from east or rolled rounds and more particularly to a novel form of expanding and elongating mill.

5 A novel method of expanding a pierced billet without any substantial increase in length is disclosed in my copending application, Serial No.

660,716, filed March 14, 1933. It is desirable under some conditions to secure a substantial increase in length as well as an increase in diameter. This increase in length is necessarily accompanied by a corresponding decrease in crosssectional area of the billet and a reduction in wall thickness. It is, therefore, obvious that the l5 pierced billet to be expanded and elongated can be shorter and heavier in wall than would be the case if no reduction in cross-sectional area-is made in the expanding operation. a

By producing short. and heavy walled pierced billet stock less work' is required-in the preparation for subsequent expanding and elongating. In some instances, an additional elongating operation in the preparation of tubular stock for subsequent expanding and elongating is entirely obviated. Another advantage is that the loss of heat of the billet between the piercing and expanding operations is considerably reduced. It is therefore highly desirable to subsequently expand and elongate previously pierced thick walled billets.

In the practice of my invention I employ a pair of conical working rolls disposed opposite each other with the billet between. Intermediate the working rolls are a pair of power driven guide rolls also disposed at opposite sides of the billet as viewed in end elevation. To complete the working pass a conical mandrel or plug is positioned in the roll pass formed by the two work rolls and the two guide rolls. The axis of each work roll projected on a horizontal plane through the longitudinal axis of the mill lies at an angle to said mill axis. A horizontal plane through each work roll axis is parallel to but on opposite sides of the horizontal plane through the axis of the mill. The axes of the guide rolls are transverse to the longitudinal axis of the mill and may be at right angles to said mill axis which makes the mid-plane through the guide rolls parallel to a vertical plane through the longitudinal axis of the mill. The mid-plane of the guide rolls may, however, be at an angle to the said vertical plane through the axis of the mill. The conical work rolls and power driven guide rolls employed in my invention form a roll pass having both a converging and diverging section.

The converging section is employed to grip and rotate the billet while advancing it forward into the most constricted portion of the pass or gorge. The conical plug projects forwardly into this gorge, which is adjacent the point where 5 the inner wall of the pierced billet contacts with the plug, and the rolling action starts on the hot metal. In the diverging portion of the roll pass the distance, in a transverse plane, between work roll faces increases at the same rate as the 10 corresponding diameter of the work roll increases. This arrangement provides that the ratio of peripheral speed of the rolls to the peripheral speed of the billet is substantially the same for all transverse sections through billet and work rolls.

The diameter of the plug increases at such a rate that the metal pass is decreased in width, thereby producing a gradual reduction in wall thickness of the billet being expanded. This reduction in wall for the early portion of the ex- 20 panding pass would be at a rate to provide the desired rate of increase in diameter, but with no appreciable reduction in cross-sectional area of billet metal. This expansion without change of a section area proceeds until a substantial part of 25 the total increase in diameter is produced. The taper or expansion of the plug is then increased for the last portion of the large end of the plug in order to reduce wall thickness at a greater rate than necessary to maintain uniform sec- 30 tion area. As the section area is reduced at this increased rate the metal tends to flow radially and produce a much greater diameter, but the guide rolls are positioned at this section of the pass and because of their high relative-speed to- 35 wards the outlet of the pass and the pressure contact with the metal divert this potential circumference into length.

It will be apparent to those skilled in the art that in order to cause metal of the billet to flow 40 -forwardly at a greater rate than the work rolls tend to impart in this direction the metal must be free to flow or an upsetting action takes place.

It is, therefore, desirable to locate the elongating section of the passnear the outlet where the 45 metal displaced forwardly by the guide rolls is free to move in this direction without being retarded by metal that is restrained from longitudinal movement by the work roll grip.

One object of the present invention is the pro- 50 vision of a novel apparatus for expanding and elongating previously pierced billets, and in which the usual twist of the metal of the work-piece is reduced to a minimum.

Another object is to provide means to enable 55 a more satisfactory and complete expansion and elongation ofa previously pierced billet, obviating the necessity of the usual separate elongating operation. v A further object of the invention is to provide a novel apparatus whereby a previously pierced billet is expanded and/or elongated under conditions enabling the perfect control of relative speeds between the working rolls and work-piece. A still further object is to provide suitable means enabling the expansion and elongation of a previously pierced billet and in which at least a part of the billet or work-piece is made to expand without. material change in its cross-sec- 1 tube feed.-

Referring more particularly to the drawings, in Figure 1 thereis disclosed an end elevation of the expanding and elongating mill of my inven-' tion. This mill comprises a pair of conical working rolls 2 and power driven guide rolls "3, forming a roll pass surrounding a tubular work-piece 4. A conical mandrel or plug is disposed in the interior of the tubular work-piece l and is mounted ona bar 6 for rotation therewith, but

is prevented from longitudinal movement.

Figure 3 of the drawings discloses a composite view showing the relationship of one of the conical work rolls and one of the guide rolls to the mandrel and the tubular work-piece. As before stated, in this yiew the section of the guideroll 3 and a portion of the work-piece 4 are both shown in a plane substantially 90 degrees from their true positions in the mill. This has been done for the purpose of illustrating more clearly the relationship of all of the work surfaces to the workpiece. Thecontour of the forward portion of the conical mandrel or plug 5 is such that its-relationship to the diverging portion 2 of the work pass will provide that the decrease in wall thickness is compensated for by an increase in workpiece diameter, so that while in this portion of the work roll pass its wall thickness is actually decreased, the cross-sectional area of the wall will not be reduced, with the result that the workpiece does not increase substantially in length throughout this portion of the-pass. It is to be noted, however, that the work-piece will receive a slight reduction in -diameter in the converging portion 2 of the work rolls prior to its contact with the mandrel. This will, of course, result in a slight ovality prior to the expanding operation. I The rearward portion 5 of the conical mandrel or plug is increased in diameter in such a ratio to the increase in diameter of the work rolls 2 as to provide a metal pass in which the workpiece is further expanded and its wall thickness aoaaicv materially reduced. This will mean, of course, that in this portion of the work pass the crosssectional area of the work-piece will be reduced, with the result that elongation will be obtained. The working surfaces of the guide rolls 3 contact 5 with the work-piece in this portion of the work pass, which will obviously materially assist the elongation. At the last point of contact of the divergingportions '2 of the work rolls and closely adjacent the extreme rearward portion of the conical mandrel 5 a portion 5 of the said plug is so arranged with respect to the various work rolls and guide rolls as to provide a portion of the work pass in which the work-piece is reeled" and rounded-up.

The work rolls are so proportioned that their surface speed bears a substantially constant, ratio to the surface speed of the work-piece at all transverse sections of the expanding pass, which includes those portions in which elongation and reeling takes place.

Referring to Figure 4 of the drawings, I have shown a sectional and enlarged View of a modification of the invention in which the guide rolls 3 are assisted in their restraint of the ovallty of the work-piece by stationary guiding members 3. These guiding members 3* are positioned on diametrically opposite sides of the working roll pass and extend only throughout that portion thereof in which elongation takes place and are restrained against movement in any direction by any, suitable means. In practice, it is found that while the stationary guiding members 3 are desirable for their additional restrainfiagainst superfluous ovality and particularly while working thin walled work-pieces, satisfactory results can be obtained by using the guide rolls 3 alone.

It will be obvious to those skilled in the art that the reducing section 5 of the conical mandrel may be extended towards the forward end 40;

of the plug any desired amount with correspond ing reduction in the zone wherein constant crosssectional area is maintained. In the extreme, this reducing section might be extended from the point of initial expansion to the outlet of the 45,

pass, which will accomplish a constant expansion and elongation. In practicing this form of my invention it will readily follow that the guide rolls should contact the work-piece throughout the entire portion of the work pass in which elongation takes place. I

While I. have shown and described several speciflc embodiments of my invention, it will be understood that I do not wish to'be limited exfactly thereto, since various modifications may be made without departing from .the scope of my invention, as defined in the following claim.

I claim: Apparatus ,for expanding and elongating tubular work pieces comprising a plurality of metal working rolls in combination with a tapered mandrel forming a metal pass in which the forward part of the expanding portion of the work piece is maintained at uniform cross sectional area without elongation, and power-actuated guide rolls for limiting the circumferential growth of the work piece in the rearward portion of the pass and diverting the metal thereof longitudinally to produce elongation.

BRYANT BANNISTER. 

